1. Field of the Invention
The present invention relates to a delivery member. More particularly it relates to a delivery member used in paper delivery members of office automation machinery, home electric apparatus, printers, etc., or at their parts through which film sheets, plastic sheets and other sheet-like mediums or paper are delivered. It also relates to an apparatus making use of such a member.
2. Related Background Art
Delivery members hitherto used, such as roller members used for paper transport in office automation machinery, home electric apparatus, printers, etc. are exemplified by those comprising a steel material whose surface is plated, thereafter covered with rubber and then coated with Teflon (trademark), those comprising a steel material whose surface is plated and then coated with aluminum oxide by electrostatic spraying or subjected to composite plating to form a coating containing SiC or diamond dust, those comprising a steel material whose surface is roughed by sandblasting or using a laser, those in which plating is applied to their surface thus roughened, and those comprising a steel material spray-coated thereon with a coating composition in which metal fine particles or fillers have been mixed.
These delivery members, when used, are further grounded through a voltage regulator so that the resistivity at the part through which paper passes (hereinafter "paper-pass part") can be controlled to be of a middle value.
The conventional delivery members, however, have the following disadvantages.
In the first place, in the case of the delivery member comprising a roller member spray-coated with a coating composition in which metal fine particles or fillers have been mixed, there is a limit in the simultaneous coating of a plurality of members by means of a set of coating robot when a high-grade surface uniformity is required as in the delivery members, even if an automation line is adopted in the manufacturing process. Moreover, the state of surfaces of coatings becomes non-uniform because of diffusion of coating compositions to cause a big problem in both the mass productivity and the surface properties.
The delivery member comprising a roll member comprised of a steel material whose surface is plated. thereafter covered with rubber and then coated with Teflon, has the problem that changes with time as a result of repeated use bring about a deformation of rubber to lower outside diameter precision and cause faulty paper feed and output. This not only lowers its commercial value but also requires a prolonged process in its manufacture, lowers operating efficiency, and results in a high production cost. Thus, there is a great problem in its mass productivity.
As for the delivery member comprising a roller member whose surface, e.g., stainless steel surface has been sandblasted to increase a coefficient of surface friction, the member has the problem that its material is so high in hardness that it is difficult to enhance work precision, also resulting in an increase in both the material cost and the manufacturing cost.
Similarly, the delivery member comprising a steel material whose surface is roughed by sandblasting tends to rust on irs surface and hence requires a treatment for rust prevention, e.g., plating, carried out in a subsequent step for the purpose of protection from corrosion. In such an instance, the plating is carried out on the sandblasted surface, having a low outside diameter precision, so that the outside diameter precision is further lowered and also the number of manufacturing steps increases. Thus this member can not be mass-produced.
In the case of the delivery member comprising a steel material whose surface is roughed using a laser to increase a coefficient of friction, only one member can be manufactured at one time when it is a roller or the like, and moreover it takes a long time for that treatment. Thus this member also can not be mass-produced.
The delivery member comprising a steel material whose surface is plated and then coated with aluminum oxide by electrostatic spraying to increase the wear resistance or hardness of its surface can not be stable in the adhesion and uniformity of aluminum oxide and the final outside diameter precision. There is also a limit in the manufacture of uniform-quality goods in large quantities and at a low cost.
Besides, the delivery member comprising a metallic member whose surface is subjected to electroless plating and then, in a subsequent step, subjected to composite plating to form a coating containing SiC or diamond dust has the problem that, for example, impurities tend to be included in a composite plating bath to make the bath unstable and hence the bath can not be durable to repeated use. Moreover, there are a disadvantage of high cost in plating solutions and a problem of a poor uniform dispersibility, bringing about a big problem in manufacturing cost.
In many instances, it is an important factor to impart conductivity to the delivery member. For example, conductive paper delivery members are used in copying machines or the like at their many paper-pass parts, and resistivity is controlled at the paper-pass parts.
Namely, in the case when a paper delivery member at a paper-pass part that comes into contact with paper has insulation properties, the paper delivery member produces triboelectricity due to friction between paper and the member in an environment of low humidity, so that toner may adhere to the paper delivery member to produce a stain on the paper. In the case when a paper delivery member at a paper-pass part has a low resistivity, the paper itself comes to serve as a low-resistive element in an environment of high humidity because of its moisture absorption, so that the charges produced may leak through a transfer guide to cause blank areas of images.
FIG. 5 is a diagrammatic illustration of the part at which the transfer guide is used in a copying machine. In conventional copying machines, as shown in the drawing, a transfer guide 14 or fixing inlet guide comprised of a Ni-coated steel material is grounded through a voltage regulator (a varistor) to have a middle voltage so that toner stains and blank areas caused by poor transfer can be prevented. This method, however, requires an increase in the number of component parts to bring about an increase in operational steps, and hence can not be mass-productive. In the drawing, the numeral 9 denotes a photosensitive member; 10, toner; 11, a transfer medium; and 13, a transfer charger.